A facility which uses a combined heat and power system (hereinafter referred to as “CHP”), or cogeneration, uses a single process to simultaneously produce both thermal energy and electrical power from a single fuel source. A typical CHP system utilizes one or more prime movers, such as a diesel engine, to drive an electrical generator. Heat which results from the generation of electricity is reclaimed and then used for other purposes such as community heating or industrial processes. Users of CHP systems can achieve dramatic increases in energy efficiency, in some cases doubling the efficiency of the system. CHP systems also provide a means for providing auxiliary power to the facility which they can use to support the facility in the event of a power failure.
Most facilities which utilize CHP also receive electrical power from a utility company which transmits electrical power to end users through dedicated utility grids from the point of production at large power plants. Due to the long distances involved in the transmission of power, as well as unexpected increases in demands placed on the utility, end users often face power quality and reliability issues. These power quality issues range from conditions such as undervoltage (sags), voltage spikes, surges, overvoltage, and noise to complete power failure. When power quality and reliability are of great importance to the end user, they often rely on uninterruptible power supplies (UPS) to provide continuous power to meet the user's needs. UPS systems range in size and functionality, however most involve some type of energy storage device, such as a battery, which provides electricity through an inverter to power the load. In the event of a power grid interruption, a UPS will provide short duration conditioned power to the user through the energy storage device. In the event that the power outage last for more than several moments, some form of on-site generated power, such as a generator powered by a reciprocating engine, is engaged to provide the conditioned power before the stored energy is depleted.
Commonly, uninterrupted power involves the coupling of the UPS system with automatic transfer switches and other components including energy storage, power generation, power converters, switches, utility interfaces, and interfaces with the end user load. In facility's which utilize multiple metered electric utility services from the utility grid, this complexity is multiplied since traditionally, each utility feed required its own dedicated UPS or CHP system. Since generation equipment is available in only discrete size ranges, the combining of devices often requires over sizing of equipment for any individual utility feed in the multi-utility service facility. The use of discrete UPS and CHP systems also results in substantial wiring between the components, increasing the potential for incompatibilities and non-ideal system performance.
While existing auxiliary power systems are suitable for their intended purposes, there still remains a need for improvements in providing auxiliary power to end users that allows them to achieve the levels of power quality, efficiency and reliability required for their loads. In particular, a need exists for a topology for an auxiliary power system that provides a single on-site generating asset and central heat recovery system.